Hip fracture represents a major health problem facing the aged; 18-27% die in the year after fracture, and as many as 40% do not return to pre- fracture levels in functional domains involving lower extremities. Changes in bone mineral density (BMD) and muscle mass and strength which are expected to follow the immobility of hip fracture are thought to be key factors in subsequent falls, fractures and disability. The primary aim of the proposed study is to describe the changes in BMD during the year following hip fracture, and to identify potentially modifiable determinants of this change. The potentially modifiable factors of major interest include: time of weight bearing relative to the fracture, timing and intensity and post-fracture and the association between functional recovery in lower extremities and post-fracture changes in BMD and muscle mass and strength. These issues will be addressed through a prospective study of community- dwelling white women, aged 65 and older, entering Union Memorial Hospital with a fresh hip fracture (N-250). BMD and muscle mass and strength will be measured at 3, 10, 60, 180 and 360 days post-fracture. Information on pre-fracture health, functional status and activity level will be obtained. Ambulatory status, physical therapy, functioning/ activity level, medical events, and falls will be monitored for one year. Data will be analyzed using multivariate techniques designed to assess the impact of prefracture functioning/activity level, time to weight bearing, and commencement, duration and frequency of physical therapy on short-and long-term changes in BMD and muscle mass and strength post-fracture. In addition, the effect of changes in BMD and muscle mass and strength on the risk of falling post-fracture will be examined. Analyses will also evaluate the relationship between post-fracture changes in bone and muscle and lower extremity functioning during the post-fracture year.